[swift-evolution] Request for Discussion: Setup closures

[crk at fastmail.com]

Agreed, the
with variable {
statements
}
Format seems quite elegant and descriptive

Thanks for your time,
Cole Kurkowski

On Dec 4, 2015, 15:43 -0600, Erica Sadun<erica at ericasadun.com>, wrote:
> I really like both approaches, although I prefer the elegance of Sean's.
>  
> -- E
>  
>  
> > On Dec 4, 2015, at 2:35 PM, Sean Heber<sean at fifthace.com(mailto:sean at fifthace.com)>wrote:
> > >  
> > > On Dec 4, 2015, at 3:27 PM, Joe Groff<jgroff at apple.com(mailto:jgroff at apple.com)>wrote:
> > >  
> > >  
> > > > On Dec 4, 2015, at 1:24 PM, Erica Sadun<erica at ericasadun.com(mailto:erica at ericasadun.com)<mailto:erica at ericasadun.com>>wrote:
> > > >  
> > > > PROBLEM: With many Apple-supplied classes, typical initializers fail to fully set up an instance for use.Here's one example:
> > > >  
> > > > let task = NSTask()
> > > > task.launchPath = "/usr/bin/mdfind"
> > > > task.arguments = ["kMDItemDisplayName == *.playground"]
> > > > task.standardOutput = pipe
> > > >  
> > > > Here's another:
> > > >  
> > > > let questionLabel = UILabel()
> > > > questionLabel.textAlignment = .Center
> > > > questionLabel.font =UIFont(name:"DnealianManuscript", size: 72)
> > > > questionLabel.text = currentQuestion.questionText
> > > > questionLabel.numberOfLines = 0
> > > >  
> > > > You end up with stodgy repetitive code that turns into a blocky hard-to-follow clump. Here are some of my complaints:
> > > > This code feels unnecessarily redundant
> > > > This code visually stacks. The task/task/task and questionLabel/questionLabel/questionLabel blocks draw attention away from the actual set-up these lines of code are intended to do.
> > > > The extra symbol verbiage goes against common Swift style. For example, when the context is clear, prefer .whitespaceAndNewlineCharacterSet to NSCharacterSet.whitespaceAndNewlineCharacterSet.
> > > > Further, if you have many instances to set up there's no clear way to differentiate unrelated set-up groups other than inserting whitespace gaps or building custom factory functions.
> > > >  
> > > > PROPOSED SOLUTION: What do you think about creating setup closuresthat modify initializers and automatically introduce self-references. For example the NSTask() initialization might look something like this instead:
> > > >  
> > > > let task = NSTask()>>{
> > > > launchPath = "/usr/bin/mdfind"
> > > > arguments = ["kMDItemDisplayName == *.playground"]
> > > > standardOutput = pipe
> > > > }
> > > >  
> > > > In this example, the braces are scoped to the instance as self, enabling the properties to entirely drop their prefixes and be grouped together for set-up.
> > >  
> > > In Smalltalk and Dart, you can do this with method cascades, which apply multiple methods to the same 'self'. In Dart they use '..' for this:
> > >  
> > > let task = NSTask()
> > > ..launchPath = "..."
> > > ..arguments = [...]
> > > ..standardOutput = pipe
> > >  
> > > The nice thing about that is that it's a bit more generally applicable than just initialization.
> > >  
> > > -Joe
> >  
> > I would also be in favor of something more generally applicable rather than making initialization more special. I think I prefer the block-style over Dart’s approach. Smalltalk uses semicolons for this, if I recall. I’m not sure I like using a special operator. I’m obviously a keyword guy.. :P
> >  
> > with let task = NSTask() {
> > launchPath = "/usr/bin/mdfind"
> > arguments = ["kMDItemDisplayName == *.playground"]
> > standardOutput = pipe
> > }
> >  
> > Also valid:
> >  
> > with someVariable {
> > func1()
> > func2(“etc")
> > }
> >  
> > Which would call func1() and func2() on the someVariable instance (which I think would be quite expected).
> >  
> > l8r
> > Sean
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